The present invention relates to a bottom bracket bearing axle mounting structure for bicycles which uses two screw caps fastened to the two opposite ends of the transverse mounting hole of the bicycle bottom bracket to hold a barrel and two rings of balls around the axle.
The bottom bracket bearing axle is the source of the power output of a bicycle, which is mounted on the bottom bracket and supported on balls and coupled with cranks and pedals for turning by the legs. The coefficient of friction between the balls and the axle has great concern with the operation of the bicycle. If the balls are not firmly retained in place during the rotary motion of the axle, the movement of the axle will become unstable. FIGS. 1 and 2 show a bottom bracket bearing axle mounting structure according to the prior art which is generally comprised of a barrel, an axle, two rings of balls, a ball bearing block, a nut, and a screw cap. The barrel comprises a longitudinal center through hole, two horn-like orifices at two opposite ends, and two ball bearings disposed between the longitudinal center through hole and the horn-like orifices. The axle comprises an outer thread and a collar near two opposite ends, and an annular groove near the collar. The rings of balls are respectively mounted around the axle and supported on the ball bearings. The ball bearing block comprises a curved bearing wall matched with one ball bearing to hold one ring of balls, an center screw hole threaded onto the outer thread of the axle. The nut is threaded onto the outer thread of the axle and stopped at one end of the ball bearing block. During the assembly, process, the screw cap is threaded into one end of the bottom bracket, then a rubber ring is mounted around the annular groove on the axle, then the ring of balls is mounted on the ball bearing of the barrel, and then the ring of balls is covered with grease, and then the barrel is sleeved onto the axle, and then the ring of balls is mounted on the ball bearing, and then the ball bearing block and the nut and the oil seal ring are respectively threaded onto the outer thread of the axle. This bottom bracket bearing axle mounting structure is complicated and inconveneint to install. When the axle is rotated, the rings of balls tend to displace, causing the axle vibrated. Furthermore, the position of the ball bearing block on the axle must be accurately calibrated so that the friction between the ring of balls and the axle can be controlled within the optimum range. However, calibrating the positioning of the ball bearing block is not an easy job and requires special techniques.
The present invention has been accomplished to provide a bottom bracket bearing axle mounting structure which eliminates the aforesaid problems. It is one object of the present invention to provide a bottom bracket bearing axle mounting structure which consists of less number of parts. It is another object of the present invention to provide a bottom bracket bearing axle mounting structure which is easy to install. It is still another object of the present invention to provide a bottom bracket bearing axle mounting structure which is stable in operation. To achieve these objects, there is provided a bottom bracket bearing axle mounting structure comprised of a barrel received in the transverse mounting hole of the bottom bracket of a bicycle to hold an axle, a first screw cap threaded into one end of the transverse mounting hole to hold a first ring of balls on a first ball bearing on the axle, and a second screw cap threaded onto one end of the barrel and into an opposite end of the transverse mounting hole to hold a second ring of balls around a second ball bearing on the axle.